Apparatus and method of page program operation for memory devices with mirror back-up of data

ABSTRACT

An apparatus and method of page program operation is provided. When performing a page program operation with a selected memory device, a memory controller loads the data into the page buffer of one selected memory device and also into the page buffer of another selected memory device in order to store a back-up copy of the data. In the event that the data is not successfully programmed into the memory cells of the one selected memory device, then the memory controller recovers the data from the page buffer of the other memory device. Since a copy of the data is stored in the page buffer of the other memory device, the memory controller does not need to locally store the data in its data storage elements.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.12/030,235 which claims the benefit of prior U.S. Provisional PatentApplication No. 60/891,115 filed on Feb. 22, 2007, the disclosures ofwhich are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates generally to semiconductor devices. Moreparticularly, the present invention relates to an apparatus and a methodfor page program operation for memory devices.

BACKGROUND

Electronic equipment uses memory devices, for example, flash memories,for storing data or information. In a memory system, a memory controllerprograms a selected flash memory device by transmitting data to a pagebuffer in a selected flash memory device where it is stored temporarily.Programming of the data from the page buffer into in the flash memorycommences and the programming result is verified and a verify result isproduced as “pass” or “fail”. Program and verify operations areperformed several times for a “program time” specified period. After theprogram time, in the event of failure, the data is re-loaded from thememory controller to resume the page program operation in the sameselected device.

A drawback is that flash memories require a long program time, forexample, to verify the program status. The memory inside of the memorycontroller must hold the initial program data in order to recover theoriginal program data in the event of program failure. The initialprogram data occupies space in the memory of the memory controller, withthe result that the memory space can not be used for other purposes.

SUMMARY

According to one aspect of the present invention, there is provided anapparatus for controlling a plurality of memory devices interconnectedin-series, each of the memory devices having a page buffer and memorycells. The apparatus comprises a data processor configured to execute apage program operation with a mirror back-up of data by: writing data tothe page buffer of a selected memory device of the plurality of memorydevices and to the page buffer of another memory device of the pluralityof memory devices; instructing the selected memory device to program thedata loaded in its page buffer into its memory cells; and determiningwhether the data is not successfully programmed into the memory cells ofthe selected memory device, recover the data from the page buffer of theanother memory device.

For example, the data processor is configured to recover the data fromthe page buffer of the another memory device by: reading back the datafrom the page buffer of the another memory device without programmingthe data into the memory cells of the another memory device.

The apparatus may further comprise data storage for storing the dataprior to writing the data to the page buffer of the selected memorydevice and to the page buffer of the another memory device.

According to another aspect of the present invention, there is provideda system comprising: a plurality of memory devices that areinterconnected in-series, each memory device having a page buffer andmemory cells; and an apparatus for controlling the plurality of memorydevices, the apparatus comprising a data processor configured to executea page program operation with a mirror back-up for data by: writing datato the page buffer of a selected memory device of the plurality ofmemory devices and to the page buffer of another memory device of theplurality of memory devices; instructing the selected memory device toprogram the data loaded in its page buffer into its memory cells; and ifthe data is not successfully programmed into the memory cells of theselected memory device, recover the data from the page buffer of theanother memory device.

According to another aspect of the present invention, there is provideda method for controlling a plurality of memory devices that areinterconnected in-series, each memory device having a page buffer andmemory cells. The method comprises: transmitting data to the page bufferof a selected memory device of the plurality of memory devices and tothe page buffer of another memory device of the plurality of memorydevices; instructing the selected memory device to program the dataloaded in its page buffer into its memory cells; and if the data is notsuccessfully programmed into the memory cells of the selected memorydevice, recovering the data from the page buffer of the another memorydevice.

For example, the step of recovering the data from the page buffer of theanother memory device comprises reading back the data from the pagebuffer of the another memory device without programming the data intothe memory cells of the another memory device.

The method may further comprise storing the data prior to writing thedata to the page buffer of the selected memory device and to the pagebuffer of the another memory device; freeing up space where the data isoccupied before determining whether the data has been successfullyprogrammed into the memory cells of the selected memory device.

According to another aspect of the present invention, there is provideda memory device for use as one of a set of memory devices connectedin-series. The memory device comprises: an input connection; an outputconnection; an identification of a device address of the memory device;and a device controller configured to: receive messages to enter andexit a multi-address detection mode, and enter and exit themulti-address detection mode accordingly; receive a command over theinput connection, the command comprising a device address; while not inthe multi-address detection mode, process the command only if the deviceaddress of the command matches the device address of the device; andwhile in the multi-address detection mode: i) process the command if thedevice address of the command is the same as the device address of thedevice and ii) process the command if the device address of the commandis the same as the device address of at least one other predetermineddevice.

According to another aspect of the present invention, there is provideda method in a memory device forming part of a set of memory devicesconnected in-series, the method comprising: maintaining a deviceaddress; receiving messages to enter and exit a multi-address detectionmode; receiving a command comprising a device address; while not in themulti-address detection mode, processing the command only if thedestination address matches the device address; and while in themulti-address detection mode: processing the command if the deviceaddress of the command is the same as the device address of the device;and processing the command if the device address of the command is thesame as the device address of at least one other predetermined device.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described with reference to the attacheddrawings in which:

FIG. 1 is a block diagram of an example system having an architecturefeaturing devices connected in-series to which embodiments of thepresent invention are applicable;

FIG. 2 is a schematic of example command formats for the memory devicesconnected in-series;

FIG. 3 is a schematic of an example procedure for page programming andverification;

FIG. 4 is a block diagram of two memory devices, one of which is used asa mirror back-up for data;

FIG. 5 is a block diagram of a system having an architecture featuringdevices connected in-series in which a page buffer is used as a mirrorbackup for data;

FIG. 6 is a block diagram of another system having an architecturefeaturing devices connected in-series in which a page buffer is used asa mirror backup for data;

FIG. 7 is an example timing diagram of enabling and disabling of an LSB(least significant bit) ignore mode for the system of FIG. 6;

FIG. 8 is a block diagram of the system of FIG. 6 in which a datarecovery is performed after program failure;

FIG. 9 is a block diagram showing part of the series-connected memorydevices shown in FIG. 1;

FIG. 10 is a schematic of example circuitry of a memory device shown inFIG. 9;

FIG. 11 is a flowchart of a method of program operation with a mirrorback-up;

FIG. 12 is a table of an example command set;

FIG. 13 is a table of an example operation table;

FIG. 14 is a table showing an example of a detailed command and addressformat;

FIG. 15 is an example timing diagram showing basic input timing in amemory system;

FIG. 16 is an example timing diagram showing an input sequence of bitstreams in a modular command NAND flash memory system;

FIG. 17 is an example timing diagram showing basic output timing in amemory system;

FIG. 18 is an example timing diagram showing an output sequence of bitstreams in a memory system;

FIG. 19 is a flowchart of a method of page read operation; and

FIG. 20 is an example timing diagram showing page read and burst dataread operations.

DETAILED DESCRIPTION

In the following detailed description of sample embodiments of theinvention, reference is made to the accompanying drawings which form apart hereof, and in which is shown by way of illustration specificsample embodiments in which the present invention may be practiced.These embodiments are described in sufficient detail to enable thoseskilled in the art to practice the present invention, and it is to beunderstood that other embodiments may be utilized and that logical,mechanical, electrical, and other changes may be made without departingfrom the scope of the present invention. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present invention is defined by the appended claims.

FIG. 1 shows a system according to an embodiment of the presentinvention. Referring to FIG. 1, a system 150 includes a memorycontroller 151 and a serial interconnection of a plurality (M) of memorydevices 154-1, 154-2, 154-3, . . . , and 154-M that are connectedin-series, M being an integer greater than one. The memory controller151 and the memory devices are interconnected via links having datawidth n, where n is an integer greater than or equal to one. In a caseof n being one, the interconnection link will be a serial link and in acase of n being more than one, the interconnection link will be aparallel link. The memory controller 151 is connected to the firstmemory device 154-1 of the serial interconnection. The last memorydevice 154-M is also connected to the memory controller 151 so thatfirst, second, third, . . . , and M-th memory devices 154-1, 154-2,154-3, . . . , and 154-M of the serial interconnection together with thememory controller 151 form a ring connection structure. In theillustrated example, the memory devices 154-1-154-M are flash memorydevices. Subsequent examples are also specific to flash memory. However,it is to be understood that embodiments of the present invention arealso applicable to other types of non-volatile memory devices.

In the particular example shown in FIG. 1, each of the series-connectedmemory devices 154-1-154-M is a flash memory device, such as, forexample, a NAND flash device. The flash memory device has a page bufferfor temporary storing information on data. The stored information iswritten into flash memory cells of the device in accordance with pageprogramming. Once programmed, the information stored in the page bufferis corrupted due to the verification process of the programmed cells.

The memory controller 151 has a data storage 152 and a processor 153.The data storage 152 stores various data that includes information onoperation instructions, addresses and memory data to be processed and tobe stored in the series-connected memory devices. The information onoperation instructions is used for controlling the series-connectedmemory devices. The data storage 152 is, for example, a static randomaccess memory (SRAM) or any type of embedded memory. More generally, anyappropriate data storage may be implemented. The processor 153 performsoperations of data processing and controlling of the memory devicesaccessing the data stored in the data storage 152. The memory controller151 has a plurality of connections: a command signal output connectionCIO, a command signal input connection COI, an input strobe connectionCSIO, an output strobe connection DSIO and a clock output connectionCKO.

In operation, the memory controller 151 sends a command input (CI)signal S_(C1) through the command signal output connection CIO to thefirst device 154-1 and receives a command output (CO) signal S_(C(M+1))from the last device 154-M of the serial interconnection, through thecommand signal input connection COI. Also, the memory controller 151provides a command strobe input (CSI) signal S_(CS1) through the inputstrobe connection CSIO and a data strobe input (DSI) signal S_(DS1)through the output strobe connection DSIO to the first device 154-1.Furthermore, the memory controller 151 provides a clock signal CKthrough the clock output connection CKO to all of the devices154-1-154-M in a common clock source fashion.

The memory devices 154-1, 154-2, 154-3, . . . , and 154-M have pagebuffers 158-1, 158-2, 158-3, . . . , and 158-M, respectively, and flashmemory cells 159-1, 159-2, 159-3, . . . , and 159-M, respectively. Eachof the memory devices 154-1-154-M has a signal input connection CI forreceiving the CI signal S_(Ci) (i=1 to M) from a previous device; asignal output connection CO for providing the CI signal S_(C(i+1)) to asucceeding device; an input strobe input connection CSI for receivingthe CSI signal S_(CSi) from a previous device; an input strobe outputconnection CSO for sending an output CSI signal S_(CS(i+1)) to thesucceeding device; an output strobe input connection DSI for receivingthe DSI signal S_(DSi) from the previous device; and an output strobeoutput connection DSO for sending an output DSI signal S_(DS(i+1)) tothe succeeding device.

Each of the memory devices 154-1-154-M has a unique device address (DA)that is hard wired or pre-assigned, so that one device can be selectedor designated at a time in normal operation. Example details of anarchitecture featuring devices connected in-series are provided in U.S.patent application Ser. No. 11/594,564 entitled “Daisy Chain CascadingDevices” filed Jul. 31, 2006, the disclosure of which is herebyincorporated by reference in its entirety. Other example details of anarchitecture feature devices connected in-series are provided in U.S.Provisional Patent Application Ser. No. 60/868,773 entitled “System andMethod of Operating Memory Devices of Varying Type” filed Dec. 6, 2006,the disclosure of which is hereby incorporated by reference in itsentirety. Examples of the device address assignment in a plurality ofmemory devices that are connected in-series are provided in U.S.Provisional Patent Application No. 60/787,710, filed Mar. 28, 2006; U.S.patent application Ser. No. 11/521,734 filed Sep. 15, 2006; U.S.Provisional Patent Application No. 60/802,645, filed May 23, 2006; andU.S. patent application Ser. No. 11/750,649 filed May 18, 2007, thedisclosures of which are incorporated by reference in their entirety.

In the normal operation, the memory controller 151 sends the CI signalS_(C1) containing commands. A command includes a device address (DA) andan operation code (hereinafter OP code) representing an operationinstruction. Some commands additionally include address information, andsome commands additionally include data. Each OP code is associated witha respective operation. Each command is also referred to herein ashaving a type that is associated with the OP code contained in thecommand. For example, a command containing a read OP code is referred toas a “read command”. Each of the memory devices 154-1-154-M receivescommands via its respective CI either directly from the memorycontroller in the case that a given device is the memory deviceconnected directly to the memory controller (device 154-1 in theillustrated example), or from an adjacent preceding memory device forother devices. Each of the memory devices 154-1-154-M uses itsrespective CO for forwarding on commands either to the memory controller151 in the case that a given device is the one having its outputconnected to the memory controller (device 154-M in the illustratedexample), or to an adjacent following device. A command containing awrite OP code addressed to a particular flash memory device results indata being written to a page buffer of that device, and then transferredfrom the page buffer to the flash memory cells of the memory device. Acommand containing a read OP code addressed to a particular flash memorydevice results in data being read from the flash memory cells of thememory device to the page buffer of the memory device and then beingtransferred out of the page buffer.

The memory controller 151 issues commands, each of which include adevice address (DA), a command operation code (hereinafter OP code).Some commands may additionally include address information, and somecommands may additionally include data. Each OP code is associated witha respective operation. Each command is also referred to herein ashaving a type that is associated with the OP code contained in thecommand. For example, a command containing a read OP code may bereferred to as a “read command”. For example, commands for use in theseries-connected devices are flexible modular commands, the structure ofwhich is shown in Table I:

TABLE I DA OP Code RA CA DATA 1 byte 1 byte 3 bytes 2 bytes 1-2112 bytes

In Table I, DA is a device address; OP code is an operation code; RA isa row address; CA is a column address; and DATA is write data. Examplesof commands associated with OP codes are a “burst data load” command anda “burst data read” command. There are cases of: (i) either of rowaddress or column address; (ii) neither row address nor column address;(iii) no data.

FIG. 2 is a schematic of example command formats for the memory devicesinterconnected in-series. Referring now to FIG. 2, a first commandformat 109-1 includes an ID number and an OP code. The ID number is usedto uniquely identify a selected memory device, while the OP code fieldcontains the OP code to be executed by the selected device. Commandswith the first command format 109-1 may for example be used for commandscontaining OP codes for reading a register value. A second commandformat 109-2 includes an ID number, an OP code and data. Commands withthe second command format 109-2 may for example be used for commandscontaining OP codes for writing data to a register. A third commandformat 109-3 includes an ID number, an OP code, and additionaladdresses. The additional addresses may for example include row and/orcolumn addresses for addressing a location in memory cells. Commandswith the third command format 109-3 may for example be used for commandscontaining OP codes for reading data from memory cells of a selectedmemory device. A fourth command format 109-4 includes an ID number, anOP code, additional addresses, and data. Commands with the fourthcommand format 109-4 may for example be used for commands containing OPcodes for writing data to the memory cells of a selected memory device.Note that all four example command formats 109-1, 109-2, 109-3, 109-4start with an ID number for addressing purposes. It should be understoodfrom the foregoing that the term “command” as used herein does notmerely refer to a command OP code, as a command may include an IDnumber, an OP code, additional addresses, data, or any other informationrelating to the control of an arrangement of memory devicesinterconnected in-series.

A particular example of the above-referenced command structures aretaught in commonly assigned and co-pending U.S. patent application Ser.No. 11/840,692 filed on Aug. 17, 2007 and U.S. Provisional PatentApplication No. 60/892,705 filed on Mar. 2, 2007, the contents of whichare hereby incorporated by reference in their entirety. The applicationsdisclose different command structures to distinguish core accessoperations that involve relatively long processing times from pagebuffer access operations that involve relatively short access times.Further details of the modular command structure are provided belowunder the heading “Modular Command Structure”.

Referring back to FIG. 1, each of the memory devices 154-1, 154-2,154-3, . . . , and 154-M receives commands via its respective CI eitherdirectly from the memory controller in the case that a given device isthe memory device connected directly to the memory controller (device154-1 in the illustrated example), or from an adjacent preceding devicefor other devices. Each memory device uses its respective CO forforwarding on commands either to the memory controller in the case thata given device is the one having its output connected to the memorycontroller (device 154-M in the illustrated example), or to an adjacentfollowing device. With conventional command structures, a commandcontaining a read OP code addressed to a particular flash memory deviceresults in data being read from the flash memory cells of the memorydevice to the page buffer of the memory device and then beingtransferred out of the page buffer. A command containing a write OP codeaddressed to a particular a flash memory device results in data beingwritten to a page buffer of that device, and then transferred from thepage buffer to the flash memory cells of the memory device.

FIG. 3 shows an example procedure for page programming and verification.Referring to FIGS. 1-3, an example of how a write operation is performedwill be described. It is assumed that data is to be written to thememory device 154-2. Data to be programmed (e.g., 100110 . . . 0100) isloaded into the page buffer 158 of memory device 154-2 from storageelements 152 of the memory controller 151 (step 112-1). Programming ofthe data into in an assigned row address (page direction) of the flashmemory commences (step 112-2). The programming result is verified (step112-3). A verify result is produced in the page buffer that overwritesthe page buffer contents that were written to the flash memory core with‘1 ’ states indicating pass and ‘0 ’ states indicating failure. Theprogramming operation may not pass because of defects on memory cells,wearing out of cell gate oxide or other defects. Internally, program andverify operations are performed several times for a specified periodthat is called a program time. As indicated at 112-4, the final contentsof the page buffer 158 become all ‘1 ’ states if all cells of theselected row (page direction) are programmed correctly. After theprogram time, if any ‘0 ’ value in the page buffer 158 of device 154-2still exists, then the page program has failed as indicated at 112-5. Inthe event of failure, the data is re-loaded from the storage elements152 of the memory controller 151 to resume the page program operation toa different row address (page direction) of the same selected device.

In general, flash memories have a fundamental limitation of long programtime due to cell characteristics and time used to verify the programstatus. Because of the fail probability of the page program operation,the data storage elements 152 of the memory controller 151 hold theinitial program data in order to allow the recovery of the originalprogram data in the event of program failure. The result is that theinitial program data occupies space in the data storage elements 151thereby preventing the space from being used for other purposes. It mayresult in having to wait until the page program operation andverification has completed before performing other page programoperations. A possible approach to improving performance may be toincrease the capacity of the storage elements in the memory controller,but this can be costly.

In the example system 150 shown in FIG. 1, when performing a pageprogram operation with a selected memory device, the memory controller151 loads the data into the page buffer 158 of the selected memorydevice and also into the page buffer of another memory device in orderto store a back-up copy of the data. In this example, it is assumed thatthe selected memory device is the first memory device 154-1 and theother memory device is the second memory device 154-2. More generally,the selected memory device and the other memory device may be any two ofthe memory devices 154-1, 154-2, 154-3, . . . , and 154-M. In the eventthat the data is not successfully programmed into the memory cells ofthe selected memory device 154-1, then the memory controller 151recovers the data from the page buffer 158 of the second memory device154-2. The page buffer 158 of the second memory device 154-2 is accessedindependently of the program operation. This allows the data to berecovered without having to program the data into the memory cells ofthe second memory device 154-2. Since a copy of the data is stored inthe page buffer 158 of the second memory device 154-2, the memorycontroller 151 does not need to locally store the data in its datastorage elements 152. Therefore, the memory controller 151 can free upspace in its data storage elements 152 where the data is stored beforedetermining whether the data has been successfully programmed into thememory cells of the selected memory device 154-1.

In the particular example, for the purpose of allowing the page buffersto operate as a mirror back-up, in accordance with an embodiment of theinvention, three “modular” memory device access commands are used. Thefirst is referred to as a “burst data load” command and contains a burstdata load OP code. This causes data to be written to the page buffer,but this command alone does not cause the data to be transferred to theflash memory cells. In the examples that follow, 4Xh and 5Xh are usedfor this, but more generally the command structure would be defined onan implementation specific basis. The second is referred to as a “burstdata read” command and contains a burst data read OP code. This causesdata to be read directly from the page buffer without first reading fromthe flash memory cells. In the examples that follow, 2Xh is used forthis, but more generally, the command structure would be defined on animplementation specific basis. The third is referred to as a “pageprogram” command and contains a page program OP code. This causes datathat was previously stored in the page buffer to be written to the flashmemory, destroying the contents of the page buffer in the process forverification purposes. In the examples that follow, 6Xh is used forthis, but more generally, the command structure would be defined on animplementation specific basis.

FIG. 4 shows two memory devices shown in FIG. 1. Referring to FIGS. 1and 4, two devices 120 and 127 represent two devices in the system 150and two devices are adjacent to or remote from each other in theinterconnection configuration. One of the two devices 120 and 127 isused as a mirror back-up for data.

The first memory device 120 has an input connection 139, an outputconnection 140, flash memory cells 121, a page buffer 122 and a devicecontroller 126. Similarly, the second memory device 127 has an inputconnection 141, an output connection 142, flash memory cells 128, a pagebuffer 129 and a device controller 130. The two memory devices 120, 127are any two memory devices that form part of an architecture featuringdevices interconnected in-series. For the particular example, one of thetwo memory devices 120 and 127 is used as a mirror back-up for data. Thedevice controllers 126 and 130 include any appropriate circuitry forfacilitating processing of commands. Subsequent examples will not referto any device controllers; however, it is to be understood that theywould include circuitry for processing commands.

In operation, the page buffer 122 of the first memory device 120 isloaded with data by the burst data load command (4Xh and 5Xh) throughthe input connection 139 as indicated at 123. In this example, the datais also loaded into the page buffer 129 of the second memory device 127through the input connection 141 as indicated at 137. Page programmingwithin memory device 120 is accomplished by a page program command (6Xh)as indicated at 124. The page buffer 122 is read through the outputconnection 140 using the ‘Read Device Status (D0h)’ as indicated at 125to verify whether the page programming operation was successful or not.The second memory device 127 is used as a mirror back-up for pageprogram operation in the event that page programming is unsuccessful forthe first memory device 120. A memory controller (not shown) keeps trackof which memory device is being used as the mirror back-up. In the eventof program failure, the data can be recovered from the mirror back-upthrough the output connection 142 as indicated at 138. This removes theneed for the memory controller to store the contents in its storageelements. Thus, the location used by the memory controller to store thedata prior to its being programmed to the page buffers 122, 129 can befreed up for other purposes.

The mirror function of page buffer for systems having an architecture inwhich devices are interconnected in-series will now be described withreference to FIGS. 5 and 6. FIG. 5 provides an example where the samedata is to written to two different page buffers using two separatewrite commands (i.e., one for each page buffer). In anotherimplementation, a single write command is used to write the same data totwo or more page buffers. An example of this is provided below withreference to FIG. 6.

FIG. 5 shows a system having an architecture featuring devices connectedin-series in which a page buffer is used as a mirror backup for data.Referring first to FIG. 5, a system 190 having a memory controller 191and a plurality of memory devices 193-1, 193-2, 193-3, . . . , and193-15 that are connected in-series. In the particular example, thesystem 190 includes 15 memory devices. More generally two or more may beprovided. The memory controller 191 has data storage elements 192 and adata processor 203. The memory controller 191 also has an outputconnection CIO for connecting with the first memory device 193-1, and aninput connection COI for connecting with the last memory device 199-15.The memory devices 193-1, 193-2, 193-3, . . . , and 193-15 have pagebuffers 194, 196, 198 and 190, respectively, and each of the memorydevices 193-1, 193-2, 193-3, . . . , and 193-15 has memory cells (notshown).

The memory controller 191 and the memory devices 193-1, 193-2, 193-3, .. . , and 193-15 are interconnected with serial links. Other examplesdescribed herein are also specific to serial links between consecutivedevices. However, it is to be understood that embodiments of theinvention are also applicable to architectures featuring parallel linksbetween consecutive devices. More generally, embodiments of theinvention are applicable to architectures featuring series links betweenconsecutive devices. The series links may be serial links, or parallellinks. The system 190 uses a page buffer as a mirror backup for data. Inthe illustrated example, two devices are interconnected by a link havingone I/O pin. Alternatively, a link can include a plurality of I/O pins.The memory devices 193-1, 193-2, 193-3, . . . , and 193-15 hasrespective processing circuitry for processing a signal through the CIconnection from a previous device and outputting processed result thoughthe CO connection to a next device. For simplicity, such circuitry isshown by a representing D-type flip-flop (D-FF).

For this example, it is assumed that the memory controller 191 needs towrite data to the memory cells of memory device 193-1, and that the pagebuffer 194-2 of the memory device 193-2 is available for use as a mirrorbackup. In operation, the memory controller 191 issues a first writecommand in order to load data from the data storage elements 192 intothe page buffer 194-1 of the first memory device 193-1. The loading ofthe data into the page buffer 194-1 is generally indicated at 201. Inorder to keep a back-up copy of the data in the event that the pageprogramming fails, the memory controller 191 also issues a write command(page buffer load) in order to load the same data into the page buffer194-2 of the second memory device 193-2. The loading of the data intothe page buffer 194-2 is generally indicated at 202. The memorycontroller 191 then issues a page program command to program the datathat has been loaded into the page buffer 194-1 into the memory cells(not shown) of the first memory device 193-1. In the illustratedexample, the data is not programmed into the memory cells of the secondmemory device 193-2. Instead, the data is maintained in the page buffer194-1 as a mirror back-up copy of the data in case the page programmingfor the first memory device 193-1 fails.

The memory controller 191 keeps track of which memory device 193-2 isbeing used as the mirror back-up. In the event of program failure, thedata can be recovered from the mirror back-up. This removes the need forthe memory controller 191 to store the contents in its data storageelements 192. Therefore, as soon as the page buffer loads are done, thedata storage elements 192 previously used to store the data are freed upfor other uses. The memory controller keeps track of which data storageelements 192 are free, and which are in use. In the event of success inthe page programming operation, the locations in the page buffer 194-2being used as a mirror back-up are freed up.

Note that the first memory device 193-1 and the second memory device193-2 are selected by the memory controller 191. The memory controller191 can alternatively select different memory devices. Each writecommand is addressed to a target memory device by DA.

Note that for the devices connected in-series, there is a clock cyclebased latency delay between memory devices to synchronize output result(CO) from input (CI). The latency can be determined according to thesystem and device specification. All examples assume a one clock cyclelatency between input and output. Therefore, between two adjacent memorydevices, there is a one cycle difference when input data is captured.However, it is to be understood that the clock cycle latency mayalternatively be smaller such as a half cycle, or greater such as overtwo cycles. Regardless, the memory devices take input streams with thelatency delay.

FIG. 6 shows another system having an architecture featuring devicesconnected in-series in which a page buffer is used as a mirror backupfor data. Referring to FIG. 6, a system 210 using a page buffer 214-2 asa mirror backup for data. The system 210 has a memory controller 211 anda plurality of memory devices 213-1, 213-2, 213-3, . . . , and 213-15.The memory controller 211 has data storage elements 212, which is, forexample, an SRAM. The memory controller 211 also has a data processor209, an output connection CIO for connecting with the first memorydevice 213-1, and an input connection COI for connecting with the lastmemory device 213-15. The memory devices 213-1, 213-2, 213-3, . . . ,and 213-15 have page buffers 214-1, 214-2, 214-3, . . . , and 214-15,respectively, and each of the memory devices has memory cells (notshown). The memory controller 211 and the memory devices 213-1, 213-2,213-3, . . . , and 213-15 are interconnected with links. A detailedexample of mirror backup operation for the system of FIG. 6 is describedfurther below.

In an example system, a memory device that is to function as a mirrorbackup for a given memory device is statically defined. A particularexample of such a static definition is defined in the tables below inwhich it is assumed that: for a given device having an even deviceaddress, the device that is to function as a mirror backup for the givendevice is the device having an address one greater than that of thegiven device (see Table 2) and for a given device having an odd address,the device that is to function as mirror backup for the given device isthe device having an address one less than that of the given memorydevice (see Table 3).

TABLE 2 For even device addresses, static association between DesignatedTarget Address (DAt) and Mirror Address (MA) defined by: MA = DAt + 1Designated Target Address (DAt) Mirror Address (MA) 0000 0001 0010 00110100 0101 — — — — 1010 1011 1100 1101

TABLE 3 For odd device addresses, static association between DesignatedTarget Address (DAt) and Mirror Address (MA) defined by: MA = DAt − 1Designated Target Address (DAt) Mirror Address (MA) 0001 0000 0011 00100101 0100 — — — — 1011 1010 1101 1100

In the examples defined by Tables 2 and 3 above, the designated targetdevice and the mirror device share common addresses with the exceptionof the LSB (least significant bit). More generally, in some examples,the relationship between the designated target device and the mirrordevice is used to efficiently address the two devices without requiringtwo separate commands to be sent.

A specific example of this applies to the mirror backup devicedefinitions in Tables 2 and 3 in which a new mode of operation referredto as “ignore LSB mode” in which all devices compare all bits of theaddress of each incoming command except the LSB to corresponding bits ofthe device's device address (namely all of the bits except the LSB). Insuch a mode, both a device having a given designated target address, andan appropriate mirror device will process the command. In someimplementations, a command is first sent to turn on ignore LSB mode.This can be done using an address that is processed by all devices,referred to as a broadcast address. This is followed by a command toload data to the page buffer, this resulting in the data being loaded tothe page buffer of both a designated target device and the mirrordevice. After this, ignore LSB mode is turned off again, and a commandto write the contents of the page buffer of the designated target deviceto the core memory is sent and processed only by the designated targetdevice. In another example, a different OP code is defined thatsignifies ignore LSB mode for that command. In another embodiment,ignore LSB mode is only active for at most one following command and assuch, there is no need to turn off ignore LSB mode if such a command hasbeen sent. In another embodiment, another field in a command is used tosignify ignore LSB mode.

An example of this will now be described with reference to FIG. 6 whereit is assumed that the memory controller 211 has determined to writedata to the memory cells of memory device 213-1, while using the pagebuffer 214-2 of the memory device 213-2 as a mirror backup. This examplediffers from the example of FIG. 5 in that the memory controller 211issues a single write command in order to load data from the datastorage elements 212 to both the page buffer 214-1 of the first memorydevice 213-1 and the page buffer 214-2 of the second memory device213-2. This is accomplished during an “ignore LSB mode”, where thememory devices ignore the LSB of the target device address found in thesingle write command. In this example, the memory controller 211 sendsan ‘ignore LSB’ command to all memory devices 213-1, 213-2, 213-3, . . ., and 213-15 of the devices connected in-series to inform them to ignorethe LSB of the target device address of subsequently received commands.The ignore LSB command is, for example, a ‘Write Link ConfigurationRegister’ command with an OP code of FFh that is sent to a broadcastaddress that is processed by all memory devices. Any appropriatestructure for such a broadcast command may be used; more generally, anyappropriate mechanism for enabling the ignore LSB mode can beimplemented. Various examples have been provided above.

Once the ignore LSB mode is enabled, two memory devices are selected bya single target address. For example, a page buffer load command havinga target address of “0000” will be processed by both the first memorydevice 213-1 having a device address (DA) of “0000” and the secondmemory device 213-2 having a device address of “0001”. Note that thefirst and second memory devices 213-1 and 213-2 have identical deviceaddresses with exception to the LSB. One of the two memory devices 213-1and 213-2 (e.g., the first memory device 213-1) is used as a “designatedtarget device”, while the other memory device (e.g., the memory device213-2) is used as a “mirror device”, the page buffer of which storesmirror program data. Once the page buffer load command is issued, dataloading starts. The page buffers 214-1 and 214-2 of two selected devices213-1 and 213-2 store the data thereinto. The loading of the data intothe page buffers 214-1 and 214-2 is generally indicated at 221 and 222.Prior to programming, the ignore LSB mode is reset and normal operationwhere only one memory device is selected at a time resumes. This is, forexample, accomplished by issuing another broadcasting command. Exampletiming details of the enabling and disabling of the ignore LSB mode forthe system 210 are provided below with reference to FIG. 7.

FIG. 7 shows an example timing diagram of enabling and disabling of anLSB ignore mode for the system of FIG. 6. Referring to FIGS. 6 and 7,the memory controller 211 outputs three signals: a clock signal CK; acommand strobe input signal CSI and a command input signal CI. Note thatthe CSI signal is asserted during three stages, namely, first, secondand third stages.

The first stage is indicated at 281. The memory controller 211 sends an‘ignore LSB” command to inform the memory devices to ignore the LSB ofthe target device address of subsequently received commands. The commandcontains a broadcast DA and an OP code for enabling ignore LSB mode.Here is assumed that ‘FF’ is a broadcast address that results in all ofthe memory devices in the devices connected in-series accepting andprocessing this command.

The second stage is indicated at 282. The memory controller 211transmits a command for loading data into the page buffers 214-1 and214-2 of the first two memory devices 213-1 and 213-2. The commandincludes the device identifier (ID) for the first memory device 213-1and the burst data load instruction (CMD). Since ignore LSB mode hasbeen enabled, both the first and second memory devices 213-1 and 213-2process the command and load the data into their page buffers 214-1 and214-2.

The third stage is indicated at 283. The memory controller 211 transmitsa command for disabling the ignore LSB mode. The ID is again thebroadcast ID ‘FF’.

Once the ignore LSB mode has been disabled, the memory controller 211issues a page program command to program the data that has been loadedin the page buffer 214-1 into the memory cells (not shown) of the firstmemory device 213-1. In the illustrated example, the data is notprogrammed into the memory cells (not shown) of the second memory device213-2. Instead, the data is maintained in the page buffer 214-2 of thesecond memory device 213-2 as a mirror back-up copy of the data in casethe page programming for the first memory device 213-1 fails. The secondmemory device 213-2 should not be accessed for any core operations usingthe page buffer 214-2. However, register based commands, such as status,configuration register read or write are possible. Other memory devices213-3, . . . , and 213-15 can be freely accessed.

FIG. 8 shows the system 210 of FIG. 6 in which a data recovery isperformed after program failure. Referring now to FIG. 8, a data pathfor the data recovery is generally shown at 223. At first, the programdata in mirror buffer 214-2 of the second memory device 213-2 istransmitted to the data storage elements 212 of the memory controller211 to thereby allow the memory controller 211 to recover the initialprogram data that may not have been kept in the data storage element 212due to its being used for other purpose. Next, the program datarecovered from the mirror buffer 214-2 is sent to a new page address byperforming a page buffer load and page program. This may be to anotherpage on the first memory device 213-1 or a page on another memorydevice. If it is another memory device, the process starts from scratchby reloading the data into two page buffers. Alternatively, the dataloaded into the mirror buffer 214-2 can be maintained while therecovered data is loaded into the page buffer of another memory device.The memory controller 211 keeps track of, and does not use, failedpages. In the example depicted in FIG. 8, the program data recoveredfrom the mirror buffer 214-2 is sent to the page buffer 214-1 of anothermemory device 213-1 as indicated at 224.

In the illustrated examples provided above, specific details of thememory devices for implementing the ignore LSB feature are not provided.It is to be understood that the memory devices can be implemented withany appropriate control circuitry for accomplishing the ignore LSBfeature. A specific implementation is provided below with reference toFIGS. 9 and 10 for exemplary purposes.

FIG. 9 shows part of the series-connected memory devices shown inFIG. 1. As shown, command input signal S_(Ci), input to a device 154-ifrom a previous device 154-(i−1) can be transmitted to the next device154-(i+1).

FIG. 10 shows memory device circuitry for use in a memory device of thedevices connected in-series. The memory device circuitry implements theIgnore LSB feature. Referring to FIG. 10, a memory device 154-i has aplurality of inputs including a clock input CLK for receiving the clocksignal CK, a command strobe input CSI for receiving the command strobesignal S_(CSi), a data strobe input DSI for receiving the data strobesignal S_(DSi) and a command input CI for receiving the command inputsignal S_(Ci). The memory device 154-i has a plurality of outputsincluding a command strobe output CSO for outputting the command strobesignal S_(CS(i+1)), a data strobe output DSO for outputting the datastrobe signal S_(DS(i+1)) and the command output CO for outputting thecommand input signal S_(C(i+1)) to the next device 154-(i+1).

The clock signal CK, the command strobe signal S_(CSi), the commandinput signal S_(Ci) and the data strobe signal S_(DSi) are buffered byrespective input buffers 281, 282, 283 and 284. The buffered clocksignal and command input signal are fed to a clock generator 264 whichoutputs internally generated clock signals: an ID clock signal Clkid, anOP code clock signal Clkop, an address clock signal Clkad and a dataclock signal Clkda. The ID clock signal Clkid, the OP code clock signalClkop, the address clock signal Clkad and the data clock signal Clkdaare fed to an ID register 265, an OP code register 266, an addressregister 268 and a data register 269. The appropriate fields of thecommand of the command input signal S_(Ci) are input to the ID register265, the OP code register 266, the address register 268 and the dataregister 269 in response to the respective clock signals. The OP codeheld in the OP code register 266 is fed to the OP code decoder 267 fordecoding. The OP code decoder 267 outputs one-bit signal SIGB to aone-bit register 276 and a multi-bit (m-bits: e.g., three-bit) decodedOP code signal SDOP to core logic and memory circuitry 285. The corelogic and memory circuitry 285 also receives the buffered data strobesignal.

The command input signal S_(Ci) is latched by a D-FF 251, the output ofwhich is buffered again to produce command input signal S_(C(i+1)) to beforwarded on to the next memory device 154-(i+1).

The memory device 154-i includes exclusive NOR (XNOR) logic circuitry272 that receives as input the n-bit output of the ID register 265 andn-bit contents of a device ID register 273 for holding a value of thedevice address (DA). The XNOR logic circuitry 272 has n XNOR gates thatperform bitwidth XNOR operation between the n-bit output of the IDregister 265 and the n-bit contents of the device ID register 273 andproduces an n-bit output. The LSB of the n-bit output the XNOR logiccircuitry 272 is input to one input of an OR gate 274, and the remainingbits of the n-bit output of the XNOR logic circuitry 272 are input toAND logic circuitry 275. The one-bit register 276 is provided forregistering the “ignore LSB enable bit” (in the signal SIGB) from the OPcode decoder 267. The output of the one-bit register 276 is input as asecond input to the OR gate 274, and the output of the OR gate 274 isfed as another input to the AND logic circuitry 275. The operation ofthese components is described below.

In operation, the memory device 154-i receives a command in the commandinput signal S_(Ci). Based on the timing of the command strobe signalS_(CSi) together with the clock signal CK, the clock generator 264generates internal clock signals for appropriately latching the contentsof the command to the appropriate registers. More specifically, the IDregister 265 registers the ID of the command. The OP code register 266registers the OP code. The address register 268 registers the column/rowaddresses. The data register 269 registers any data included in thecommand. In addition, the OP code decoder 267 receives the commandregistered in the OP code register 266 and decodes it. The bufferedclock signal is provided to D-FFs in the circuitry (clock signal pathsare not shown).

In the event the command is either a command containing a broadcast DA,or a command addressed to the specific device, the OP code is decodedand processed by the device. With the broadcast DA, all devices are tobe asserted and ready to receive a command. Upon receipt of a command toenter the ignore LSB mode as determined by the OP code decoder 266, theone-bit register 276 is set and thus, the “ignore LSB enable bit” is setto enable LSB ignore mode.

The ID register 265 outputs the registered DA, which is the target DA,in parallel as n-bit data. The XNOR logic circuitry 272 compares thetarget DA (that is represented by the ID number contained in thecommand) with the device ID held in the device ID register 273 on a bitfor bit basis. If the target DA and the device ID are identical, thenthe output of the XNOR logic circuitry 272 will be all ‘1’s. The LSB ofthe comparison is fed into the OR gate 274, while the other bits are fedinto the AND logic circuitry 275. The LSB of the comparison being “high”is sufficient for the OR gate 274 to have a “high” output. The OR gate274 is also fed with the “ignore LSB enable bit” of the one-bit register276. The “ignore LSB enable bit” of the one-bit register 276 being“high” is also sufficient for the OR gate 274 to have a “high” output.Therefore, if the “ignore LSB enable bit” of the one-bit register 276 ishigh, then it does not matter whether the LSB of the target DA matchesthe LSB of the device ID. Rather, the non-LSB bits matter. The AND logiccircuitry 275 outputs an ID match signal 277 that indicates whetherthere is a match between the target DA and the device ID. This will betrue if all of the n inputs to the AND logic are high. During ignore LSBmode, this will be true if other (n−1) bits except for the LSB matchduring the ignore LSB mode. When not in ignore LSB mode, this will betrue if all n bits match. The ID match signal 277 from the AND logiccircuitry 275 determines whether the memory device 154-i executes thecommand. Upon receipt of a command to exit the ignore LSB mode, theone-bit register 276 is cleared. The ID match signal 277 is provided tothe core logic and memory circuitry 285 and an AND gate 278. The outputof the one-bit register 276 is input to an inverter 279, the invertedoutput signal of which is provided to the AND gate 278, the AND logicoutput signal of which is fed to multiplexers 254 and 256.

When there is no match between the target DA and the device ID, the IDmatch signal ID match signal 277 is “low” and the multiplexer 254 isselected to its “0” input. Therefore, the latched command input signalis provided as the command input signal SC(i+1) to the next device154-(i+1). Also, the latched command strobe signal is provided throughthe multiplexer 256 as the command strobe signal SCS(i+1) to the nextdevice 154-(i+1). Thus, there is no ID match, the device 154-1 is notthe target device and the command input signal SCi and the commandstrobe signal SCSi are forwarded to the next device 154-(i+1). If thedata strobe signal is input (e.g., in the data read mode operation), thelatched data strobe signal is provided through the multiplexer 255 asthe data strobe signal SDS(i+1) to the next device 154-(i+1), regardlessof the status of the ID match signal ID match signal 277. With no IDmatch, the core logic and memory circuitry 285 is not activated.

When there is a match between the target DA and the device ID duringignore LSB mode (i.e., the output of the one-bit register 276 is“high”), the ID match signal 277 is “high”, the core logic and memorycircuitry 285 is activated. However, the output signal of the inverter279 is “low” and the “0” inputs of the multiplexers 254 and 256 areselected. The input signal is provided as the command input signalS_(C(i+1)) to the next device 154-(i+1). Also, the command strobe signalis provided as the command strobe signal S_(CS(i+1)) to the next device154-(i+1).

When there is a match between the target DA and the device ID duringnon-ignore LSB mode (i.e., the output of the one-bit register 276 is“low”), the ID match signal 277 is “high”, the core logic and memorycircuitry 285 is activated and the decoded OP code of the decoded signalSDOP from the OP code decoder 267 is executed to operate in accordancewith the command instruction. The output signal of the inverter 279 is“high” and the AND logic output signal of the AND gate 278 is “high”.The “1” inputs of the multiplexers 254 and 256 are selected. If theinstruction is a data read, the core logic and memory circuitry 285executes the read command and in accordance with the addresses of rowand/or column, data is read from the memory therein (not shown). Theoutput data DATAout from the core logic and memory circuitry 285 isprovided as the command input signal S_(C(i+1)) to the next device154-(i+1).

The examples presented above show how two memory devices can process asingle command when they have identical device addresses with exceptionto the least significant bit. This is accomplished while the memorydevices are in an ignore LSB mode. More generally, embodiments of theinvention allow for two or more memory devices to process a singlecommand based on the target address of the single command. For example,in another embodiment, the memory devices enter a multi-addressdetection mode. This may occur for example if the memory controllerbroadcasts a first message instructing each memory device to enter themulti-address detection mode. While in the multi-address detection mode,upon receiving a command having a destination address that differs fromthe device address, the memory device conditionally processes thecommand based on the destination address. At some later time, the memorydevices exit the multi-address detection mode. This may occur forexample if the memory controller broadcasts a second message instructingeach memory device to exit the multi-address detection mode. Themessages broadcasted for entering and exiting the multi-addressdetection mode are, for example, a write link configuration registercommand comprising an op-code of FFh.

There are many ways for a memory device to conditionally process thecommand based on the destination address. In some implementations, thememory device maintains an identification of an alternative deviceaddress. If the target device address of the received command matchesthe alternative device address, then the memory device processes thecommand. In other implementations, the memory device conditionallyprocesses the command if the destination address differs from the deviceaddress in a predefined manner. For example, the memory device processesthe command if the destination address differs from the device addressonly by a single predefined bit. The single predefined bit can be theleast significant bit, examples of which have been provided above.Alternatively, the single predefined bit is some other bit.

FIG. 11 shows a method of program operation with a mirror back-up. Thismethod can be implemented by a memory controller, for example by thememory controller 211 shown in FIG. 6.

Referring to FIGS. 6 and 11, at step 311 the memory controller 211 sendsan “ignore LSB” command to all memory devices 213-1, 213-2, 213-3, . . ., and 213-15 connected in-series to inform them to ignore the LSB of thetarget device address to be received. In step 312, the memory controller211 sends a target device address as part of a command to write to thepage buffer. In a particular example, assume that the target deviceaddress is ‘0000 ’, namely the device address of device 213-1 of FIG. 6.With that address, both devices 213-1 and 213-2 will process the commandwhile in ignore LSB mode. More generally, for a given target deviceaddress, two of the devices will process the command. The command towrite to the page buffer includes data to be written. With deviceaddress matching, the data is latched by both memory device 213-1 andmemory device 213-2. Thus, the transmitted data is loaded into the pagebuffers of both devices only (step 312). This is accomplished using asingle command.

Subsequently, the memory controller 211 sends a “normal DA set” commandto all memory devices 213-1, 213-2, 213-3, . . . , and 213-15 to informthem to no longer ignore the LSB of the target device address found inreceived commands (step 313). Then, the memory controller 211 startspage programming for the designated device by sending a page programaddressed to that device (step 314). If the memory controller 211determines that the page programming is successful (YES at step 315),then processing ends. The page programming determination is performed byreading the program status from the page buffer. If the memorycontroller 211 determines that there is a program failure (NO at step315), then the memory controller 211 re-loads the program data from thepage buffer of the mirror memory device 213-2 (step 316). The programdata is stored locally within data storage elements of the memorycontroller.

Next, the memory controller 211 loads the program data back into thepage buffer of the designated memory device at step 317. Processingcontinues at step 314 by retrying to program the data into the memorycells of the designated memory device, details of which have also beenprovided above. In this example, it is assumed that another attempt toprogram the data into the same memory device is made. Alternatively, thedata can be programmed into the memory cells of another memory device.Also, in this example, it is assumed that the mirror backup copy ismaintained in the same place (device 213-2 for this example) until asuccessful page program operation is completed. Alternatively, a mirrorbackup copy can be made in a different location.

In some examples, the systems described herein are implemented using aflexible modular command structure, example details of which havealready been provided. Further example details are provided in thissection with reference to FIGS. 12 through 20. It is to be understoodthat the details provided in this section are very specific forexemplary purposes only.

FIG. 12 is a table of an example command set for flash memory withmodular command in byte mode. The table includes 15 operations: PageRead, Page Read for Copy, Burst Data Read, Burst Data Load Start, BurstData Load, Page Program, Block Erase Address Input, Page-pair EraseAddress Input, Erase, Operation Abort, Read Device Status, Read DeviceInformation Register, Read Link Configuration Register, and Write LinkConfiguration Register (device specific), and Write Link Configuration(broadcast). Each operation has a command including a Device Address(DA) (1 Byte) and an Operation (OP) Code (1 Byte). Some commands includea Row Address (3 Bytes), a Column Address (2 Bytes), and some commandsinclude Input Data (1 to 2112 Bytes). ‘X’ is ‘0h’ for “Bank 0”. ‘X’ is‘1h’ for “Bank 1” where it is assumed for this specific example thateach device has two memory banks. More generally each device has atleast one memory bank. For the last command in the table, namely thewrite link configuration (broadcast), the device address is set to “FFh”to indicate a “broadcasting” command.

FIG. 13 is an example operation table. The table includes modes for eachof a plurality of combinations of /RST (complement of a reset signal),/CE (complement of a chip enable signal), CSI (command strobe input),and DSI (data strobe input). The modes include Command Data Packet, ReadData Packet, NOP (NO Operation), Standby, and Reset.

All commands, addresses, and data are shifted in and out of the memorydevice, starting with the most significant bit (MSB). Command input (CI)signal is sampled at the positive or negative clock edge (i.e., at thecrossing point of clocks—CK and /CK) while the command strobe input(CSI) signal is “high”. Each command includes a 1-byte device address(DA) and 1-byte OP code and/or column-address/row-address/data-inputbytes if necessary. Once the CSI transits logic “high”, the 1-byte DA(Device Address) is shifted into a DA register, and then the 1-byte OPcode is shifted into an OP code register. In so doing, the mostsignificant bit (MSB) starts first on the CI signal and each bit islatched at the crossing of clocks CK and /CK while CSI is logic-HIGHstate. However every input sequence in byte mode starts at a rising edgeof clock CK (=falling edge of /CK). Depending on the command, the OPCode are followed by address bytes, data bytes, both or none as shown inFIG. 12. For this example, the address cycle has a 2-byte column addressand 3-byte row address. FIG. 14 shows a definition of an example commandand address format including the position of each bit.

For the memory devices connected in-series, a special device address(=FFh) is assigned for “Broadcast” operation. More generally, theaddress that is defined for broadcast mode operation can be defined onan implementation specific basis. This “Broadcast Device Address” may beused with any command. However, using the broadcast device address (FFh)along with the “read-type” commands is not recommended because the readdata from the last device is the only valid output data.

In some implementations, the signal bus on a modular command Flashdevice is fully multiplexed as command, address and data all share thesame pin(s). The CSI signal's logic-high state validates the commandinput (CI) signal which can be an n-bit wide signal containingmultiplexed command/address/data information for the memory device. Ifthe CSI signal stays in logic-low state, device ignores signal inputsfrom CI pins. The command input sequence normally consists of one-byteDA (Device Address) latch cycles, one-byte command latch cycles, addresslatch cycles (=3-bytes for row address or 2-bytes for column addresses)and/or data-input latch cycles up to 2,112 bytes. In 1-bit link mode,four clock-cycles at DDR (double data rate) make one byte of a serialpacket. In 2-bit link mode, two clock-cycles at DDR (double data rate)make one byte of a serial packet. In 4-bit link mode, one clock-cycle atDDR (double data rate) makes one byte of a serial packet. Every set ofcommand instructions may be followed by two extra CK and /CK transitionsafter CSI makes a HIGH to LOW transition. In some embodiments, an extranumber of CK and /CK transitions after CSI transitions to low are usedthat are equal in number to 2+# of devices in the architecture withdevices connected together in-series. Every input sequence defined inFIG. 12 is “byte-based”, which means that CSI and CI should be valid forthe unit of 8-latch cycles (=4 clock cycles at double data rate). If CSImakes a HIGH to LOW transition before the completion of byte,corresponding command and/or address sequences will be ignored bydevice. For the case of data input sequence, the last incomplete byte ofinput data will be ignored, but prior complete byte(s) of input datawill be valid.

FIG. 15 is an example timing diagram showing basic input timing. AllDA/Command/Address/Data-Inputs are asserted continuously through CIport(s) and captured on the crossing of clocks CK and /CK when /CE is“low” and the CSI signal is “high”. The input data is shifted into thememory device, most significant bit (MSB) first on CI, each bit beinglatched at the crossing of clocks CK and /CK. An input sequence of bitstreams is shown in FIG. 16. Every input sequence in byte mode starts atrising edge of clock CK as shown. Any input with incomplete byte will beignored.

FIG. 17 is an example timing diagram showing basic output timing. Theoutput on the command output (CO) is synchronously shifted out at thecrossing of clocks CK and /CK when /CE is “low”, and the DSI signal is“high”. FIG. 18 shows an example output sequence in byte mode. Theoutput data is shifted from the memory device, most significant bit(MSB) first on the CO signal, each bit being synchronized at thecrossing of clocks CK and /CK. The DSI signal is activated referenced tothe rising edge of CK so that every output sequence in byte mode startsat rising edge of CK with 1 clock read latency (=tOL) as shown in FIG.17.

Two representative commands to show the feature of modular commands aredescribed below, namely a Page Read (DA & 0Xh) and a Burst Data Read (DA& 2Xh) command. FIG. 19 shows a flowchart involving the use of thesecommands, and FIG. 20 shows an example command sequence.

With reference to FIG. 19, to enter the Page Read mode, at step 411 thememory controller issues the PAGE READ (DA & 0Xh) command to the commandregister over the CI along with three row address bytes. Issuing DA &0Xh to the command register starts the address latch cycles at step 412.Three bytes of row address are input next. The internal page readoperation starts once the address latch cycles are finished. The 2,112bytes of data within the selected page are sensed and transferred to thepage buffers in less than tR (transfer time from cell array to pagebuffers). The status register can be checked at step 413. After tR, aBURST DATA READ (DA & 2Xh) command (described in further detail below)along with two bytes of column address can be issued at step 414 andthen the DSI signal can be enabled in order to read out page buffers'data, starting from the given column address, over the CO until the DSIsignal goes low. If a user wants to monitor the internal page readstatus to determine whether the transfer from the cell array to pagebuffers is complete or not, the READ DEVICE STATUS (DA & D0h) commandcan be issued. Modular command flash has an 8-bit status register thatthe software can read during device operation.

The core access operations such as page read, page program and blockerase take long time and their processing times are varied according toPVT (Process/Voltage/Temperature) change. So, whenever issuing coreaccess commands, a user can monitor the status of each operation afterasserting command without interrupting internal operations. The otherpurpose of the status register is to check whether or not the pageprogram and block erase are performed without fail. In case of fail, anew row position is determined by the memory controller and it issues anew command containing new row address to write the same data that waswritten to the old row location that failed to be written. Withoutmonitoring the status register, the memory controller does not know thatthe program and erase operations are done without fail.

After READ DEVICE STATUS (DA & D0h) command, using DSI, all 8-bit statusis read from the status register until DSI goes to low. After the BURSTDATA READ (DA & 2Xh) command has been issued and then DSI goes to high,the serial output timing as shown in FIG. 20 will result in outputtingdata at step 415, starting from the initial column address. The columnaddress will be automatically increased during outputting data. At step416, there is ECC generation. If the ECC is verified at step 417, thenthe page read is completed. Otherwise, at step 418 there is an error.

The BURST DATA READ (DA & 2Xh) command referred to above enables theuser to specify a column address so the data at the page buffers can beread starting from the given column address within the selected pagesize while DSI is high. The burst data read mode is enabled after anormal PAGE READ (DA & 0Xh) command and page loading time (=tR). TheBURST DATA READ (DA & 2Xh) command can be issued without limit withinthe page. Every BURST DATA READ command can have same or differentcolumn address from the previous BURST DATA READ command. Only data onthe current page buffers can be read. If a different page is to be read,a new PAGE READ (DA & 0Xh) command should be issued. And after tR, a newBURST DATA READ (DA & 2Xh) command can be issued to access new pagedata.

In the embodiments described above, the device elements and circuits areconnected to each other as shown in the figures, for the sake ofsimplicity. In practical applications of the present invention,elements, circuits, etc. may be connected directly to each other. Aswell, elements, circuits etc. may be connected indirectly to each otherthrough other elements, circuits, etc., necessary for operation of thememory devices or apparatus. Thus, in actual configuration of devicesand apparatus, the elements and circuits are directly or indirectlycoupled with or connected to each other.

The above-described embodiments of the present invention are intended tobe examples only. Alterations, modifications and variations may beeffected to the particular embodiments by those of skill in the artwithout departing from the scope of the invention, which is definedsolely by the claims appended hereto.

1. An apparatus for controlling a plurality of memory devicesinterconnected in-series, each of the memory devices having a pagebuffer and memory cells, the apparatus comprising a data processorconfigured to execute a page program operation with a mirror back-up ofdata.
 2. A method for controlling a plurality of memory devices that areinterconnected in-series, each memory device having a page buffer andmemory cells, the method comprising: transmitting data to the pagebuffer of a selected memory device of the plurality of memory devicesand to the page buffer of another memory device of the plurality ofmemory devices; instructing the selected memory device to program thedata loaded in its page buffer into its memory cells; and recovering thedata from the page buffer of the another memory device.